This invention relates to a process for producing glucomannan gel particles which are useful as a deposit-cleaning agent to be formulated into hygienic and cosmetic preparations.
As is well-known, dental pastes generally contain a particulate material such as calcium carbonate, calcium phosphate, calcium sulfate, aluminum hydroxide or silica for removing deposit from the tooth by a scrubbing or exfoliating effect. In order to minimize damages to the enamel and gingiva, synthetic polymer beads have also been used. A particulate material is also used in cosmetic preparations. JP-A-06033416 discloses a skin-cleansing preparation containing a cross-linked polymer bead having a certain degree of elasticity.
The known scrubbing agents are comprised of a hard particulate material which remains hard when incorporating into hygienic and cosmetic preparations. It would be desirable to have a particulate material which, in use in the hygienic or cosmetic preparation, has a relatively soft layer on at least surfaces thereof to minimize damages to the tissue to be cleaned while retaining physical properties as a whole sufficient to exhibit scrubbing or exfoliating effects.
Applicant has disclosed in JP 2000-344801A and U.S. Pat. No. 6,558,652 a process for producing glucomannan particles which are useful as a deposit-cleaning agent to be formulated into hygienic and cosmetic preparations. The process comprises the steps of adding a glucomannan-rich flour to an aqueous ethanol containing about 40 to 50% of ethanol, allowing the flour particles to swell in the aqueous ethanol, treating the swollen flour particles with an alkali to form gelled flour particles, separating the gelled flour particles from the liquid; and drying the gelled particles. The resulting gel particles are hard and insoluble in water but swell with water to form a soft skin layer surrounding a hard core portion.
It has been found that this process suffers from certain disadvantages. First, the particle size of the resulting gel particles depends on the particle size of the starting glucomannan-rich flour and not controllable arbitrarily to a particle size suitable for particular applications. Second, excessive swelling of the starting flour may cause the dried gel particles to be completely swellable with water to form soft swollen particles free from hard core portions.
A need exists for providing a process for producing glucomannan particles which can eliminate or ameliorate the above disadvantages.